A Fast and Reliable Start-up Strategy for Three-Phase DAB Power Converters

The three-phase dual active bridge (3p-DAB) converter is a promising topology for dc conversion systems, thanks to its high power density, bidirectional power flow, and soft-switching capabilities. However, how to achieve fast while reliable start-up respecting the permissible current limit remains challenging. In this work, we propose a simple and effective start-up strategy for 3p-DAB converters. First, by simply manipulating the switching positions, the initial dc-bias current is successfully eliminated. Then, the process of fast start-up under current limits is formulated as an inequality-constrained problem, for which we solve the closed-form analytical expression. This expression is then segmented via a newly proposed coordination transform, to bridge the control parameters and system states. With a simple segmental comparison, the global optimal phase-shift ratio and duty cycle to assign to the converters are obtained. Experimental results validate the effectiveness of the proposal and demonstrate its considerable improvements over the state-of-the-art techniques.